This invention relates to azeotrope-like compositions that include 1,1,1,3,3-pentafluoropropane and at least one hydrocarbon selected from the group n-pentane, isopentane, cyclopentane, n-hexane and isohexane. The compositions of the invention are useful as blowing agents in the manufacture of rigid and flexible polyurethane foams and polyisocyanurate foams as well as aerosol propellants.
Rigid polyurethane and polyisocyanurate foams are manufactured by-reacting and foaming a mixture of ingredients, in general an organic polyisocyanate with a polyol or mixture of polyols, in the presence of a volatile liquid blowing agent. The blowing agent is vaporized by the heat liberated during the reaction of isocyanate and polyol causing the polymerizing mixture of foam. This reaction and foaming process may be enhanced through the use of various additives such as amine or tin catalysts and surfactant materials that serve to control and adjust cell size and to stabilize the foam structure during formation. Foams made with blowing agents such as CCl3F (xe2x80x9cCFC-11xe2x80x9d) and CCl2FCH3 (xe2x80x9cHCFC-141bxe2x80x9d) offer excellent thermal insulation, due in part to the very low thermal conductivity of CFC- 11 and HCFC- 141b vapor, and are used widely in insulation applications.
Flexible polyurethane foams are generally open-cell foams manufactured using an excess of diisocyanate that reacts with water, also included as a raw material, producing gaseous carbon dioxide and causing foam expansion. The flexible foams are widely used as cushioning materials in items such as furniture, bedding, and automobile seats. Auxiliary physical blowing agents such as methylene chloride and/or CFC-11 are required in addition to the water/diisocyanate blowing mechanism in order to produce low density, soft grades of foam.
Many foam producers have converted from chlorofluorocarbon (xe2x80x9cCFCxe2x80x9d) blowing agents, such as CFC- 11, to environmentally safer hydrochlorofluorocarbon (xe2x80x9cHCFCxe2x80x9d) agents and hydrocarbons. However, HCFCs, such as HCFC-141b, also have some propensity to deplete stratospheric ozone albeit significantly less than that of the CFCs.
Hydrocarbon agents, such as n-pentane, isopentane, and cyclopentane, do not deplete stratospheric ozone, but are not optimal agents because foams produced from these blowing agents lack the same degree of thermal insulation efficiency as foams made with the CFC or HCFC blowing agents. Further, the hydrocarbon blowing agents are extremely flammable. Because rigid polyurethane foams must comply with building code or other regulations, foams expanded with a blowing agent composed only of hydrocarbons often require addition of expensive flame retardant materials to meet the regulations. Finally, hydrocarbon blowing agents are classified as Volatile Organic Compounds and present environmental issues associated with photochemical smog production in the lower atmosphere.
In contrast to the foregoing blowing agents, hydrofluorocarbons (xe2x80x9cHFCsxe2x80x9d) such as 1,1,1,3,3-pentafluoropropane (xe2x80x9cHFC-245faxe2x80x9d) do not deplete stratospheric ozone. This invention provides azeotrope-like compositions based on HFC-245fa and hydrocarbons for use as blowing agents for polyurethane-type foams.
Azeotropic blowing agents possess certain advantages such as more efficient blowing than the individual components, lower thermal conductivity or K-factor, and better compatibility with other foam raw materials. Additionally, azeotropic or azeotrope-like compositions are desirable because they do not fractionate upon boiling or evaporation. This behavior is especially important where one component of the blowing agent is very flammable and the other component is nonflammable because minimizing fractionation during a leak or accidental spill minimizes the risk of producing extremely flammable mixtures.
This invention provides azeotrope-like compositions that are environmentally safe substitutes for CFC and HCFC blowing agents, that have a reduced propensity for photochemical smog production, and that produce rigid and flexible polyurethane foams and polyisocyanurate foams with good properties. The invention also provides blowing agent compositions with reduced flammability hazards compared to hydrocarbon blowing agents.
Foams made with the blowing agent compositions of this invention exhibit improved properties, such as thermal insulation efficiency, improved solubility in foam raw materials, and foam dimensional stability, when compared to foams made with hydrocarbon blowing agents alone. Although the compositions of the invention contain a hydrocarbon, it is present as a minor component and, overall, the compositions are nonflammable.
This invention provides azeotrope-like compositions comprising 245fa and at least one hydrocarbon selected from the group consisting of n-pentane, isopentane, cyclopentane, n-hexane, isohexane, and mixtures thereof that are useful as blowing agents for polyurethane and polyisocyanurate foams.
For azeotrope-like mixtures containing n-pentane, the azeotrope-like compositions comprise from about 5 to about 70 percent by weight n-pentane and from about 95 to about 30 percent by weight HFC-245fa and have a boiling point 9xc2x11xc2x0 C. at 745 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 35 percent by weight n-pentane and from about 95 to about 65 percent by weight HFC-245fa and have a boiling point of 9xc2x10.5xc2x0 C. at 745 mm Hg.
For azeotrope-like mixtures containing isopentane, the azeotrope-like compositions comprise from about 5 to about 70 percent by weight isopentane and from about 95 to about 30 percent by weight HFC-245fa and have a boiling point 7xc2x11xc2x0 C. at 748 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 45 percent by weight isopentane and from about 95 to about 55 percent by weight HFC-245fa and have a boiling point of 7xc2x10.5xc2x0 C. at 748 mm Hg
For azeotrope-like mixtures containing cyclopentane, the azeotrope-like compositions comprise from about 5 to about 60 percent by weight cyclopentane and from about 95 to about 40 percent by weight HFC-245fa and have a boiling point 11.7xc2x11xc2x0 C. at 745 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 5 to about 40 percent by weight cyclopentane and from about 95 to about 60 percent by weight HFC-245fa and have a boiling point of 11.7xc2x10.5xc2x0 C. at 745 mm Hg.
For azeotrope-like mixtures containing n-hexane, the azeotrope-like compositions comprise from about 2 to about 45 percent by weight n-hexane and from about 98 to about 55 percent by weight HFC-245fa and have a boiling point 14xc2x11xc2x0 C. at 749 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 2 to about 30 percent by weight n-hexane and from about 98 to about 70 percent by weight HFC-245fa and have a boiling point of 14xc2x10.5xc2x0 C. at 749 mm Hg.
For azeotrope-like mixtures containing isohexane, the azeotrope-like compositions comprise from about 2 to about 45 percent by weight isohexane and from about 98 to about 55 percent by weight HFC-245fa and have a boiling point 13.5xc2x11xc2x0 C. at 744 mm Hg. In a preferred embodiment, such azeotrope-like compositions comprise from about 2 to about 25 percent by weight isohexane and from about 98 to about 75 percent by weight HFC-245fa and have a boiling point of 13.5xc2x10.5xc2x0 C. at 744 mm Hg.
The azeotrope-like compositions of the invention exhibit zero ozone depletion and low global warming potential. Further, the HFC-245fa component reduces the flammability hazard associated with handling and using the blowing agent, especially when compared to the use of the hydrocarbon component alone.
Polyurethane foams expanded with the blowing agents of the invention exhibit superior performance to foams expanded with the hydrocarbon blowing agent alone. The thermal conductivity of foams prepared using the azeotrope-like compositions of the invention is lower, hence superior, when compared to the thermal conductivity of foams expanded with just the hydrocarbon blowing agent. Improved dimensional stability, especially at low temperature, is also observed.
From fundamental principles, the thermodynamic state of a fluid is defined by four variables: pressure; temperature; liquid composition; and vapor composition. An azeotrope is a unique characteristic of a system of two or more components in which the liquid and vapor compositions are equal at a stated pressure and temperature. In practice this means that the components cannot be separated during a phase change.
All compositions of the invention within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like. For the purposes of the invention, by azeotrope-like composition is meant that the composition behaves like a true azeotrope in terms of this constant boiling characteristic or tendency not to fractionate upon boiling or evaporation. Thus, in such systems, the composition of the vapor formed during the evaporation is identical, or substantially identical, to the original liquid composition. During boiling or evaporation of azeotrope-like compositions, the liquid composition, if it changes at all, changes only slightly. This is contrasted with non-azeotrope-like compositions in which the liquid and vapor compositions change substantially during evaporation or condensation.
One way to determine whether a candidate mixture is azeotrope-like within the meaning of this invention, is to distill a sample thereof under conditions, i.e., resolutionxe2x80x94number of plates, that would be expected to separate the mixture into its separate components. If the mixture is non-azeotropic or non-azeotrope-like, the mixture will fractionate, or separate into its various components, with the lowest boiling component distilling off first, and so on. If the mixture is azeotrope-like, some finite amount of the first distillation cut will be obtained which contains all of the mixture components and which is constant boiling or behaves as a single substance. This phenomenon cannot occur if the mixture is not azeotrope-like, or not part of an azeotropic system.
Another characteristic of azeotrope-like compositions is that there is a range of compositions containing the same components in varying proportions which are azeotrope-like. All such compositions are intended to be covered by the term azeotrope-like as used herein. As an example, it is well known that at different pressures the composition of a given azeotrope will vary at least slightly as does the boiling point of the composition. Thus, an azeotrope of A and B represents a unique type of relationship but with a variable composition depending on the temperature and/or pressure.
In the process embodiments of the invention, the azeotrope-like compositions of the invention may be used in methods for producing a rigid closed-cell polyurethane, a flexible open-cell polyurethane, or polyisocyanurate foam. In respect to the preparation of rigid or flexible polyurethane or polyisocyanurate foams using the azeotrope like compositions described in the invention, any of the methods well known in the art can be employed. See Saunders and Frisch, Volumes I and II Polyurethanes Chemistry and Technology (1962). In general, polyurethane or polyisocyanurate foams are prepared by combining an isocyanate, a polyol or mixture of polyols, a blowing agent or mixture of blowing agents, and other materials such as catalysts, surfactants, and optionally, flame retardants, colorants, or other additives.
It is convenient in many applications to provide the components for polyurethane or polyisocyanurate foams in preblended formulations. Most typically, the foam formulation is preblended into two components. The isocyanate, optionally certain surfactants, and blowing agents comprise the first component, commonly referred to as the xe2x80x9cAxe2x80x9d component. The polyol or polyol mixture, surfactant, catalysts, blowing agents, flame retardant, and other isocyanate reactive components comprise the second component, commonly referred to as the xe2x80x9cBxe2x80x9d component. Accordingly, polyurethane or polyisocyanurate foams are readily prepared by bringing together the A and B side components either by hand mix, for small preparations, or preferably machine mix techniques to form blocks, slabs, laminates, pour-in-place panels and other items, spray applied foams, froths, and the like. Optionally, other ingredients such as fire retardants, colorants, auxiliary blowing agents, water, and even other polyols can be added as a third stream to the mix head or reaction site. Most conveniently, however, they are all incorporated into one B Component.
Any organic polyisocyanate can be employed in polyurethane or polyisocyanurate foam synthesis inclusive of aliphatic and aromatic polyisocyanates. Preferred as a class are the aromatic polyisocyanates. Preferred polyisocyanates for rigid polyurethane or polyisocyanurate foam synthesis are the polymethylene polyphenyl isocyanates, particularly the mixtures containing from about 30 to about 85 percent by weight of methylenebis(phenyl isocyanate) with the remainder of the mixture comprising the polymethylene polyphenyl polyisocyanates of functionality higher than 2. Preferred polyisocyanates for flexible polyurethane foam synthesis are toluene diisocyantes including, without limitation, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and mixtures thereof
Typical polyols used in the manufacture of rigid polyurethane foams include, but are not limited to, aromatic amino-based polyether polyols such as those based on mixtures of 2,4- and 2,6-toluenediamine condensed with ethylene oxide and/or propylene oxide. These polyols find utility in pour-in-place molded foams. Another example is aromatic alkylamino-based polyether polyols such as those based on ethoxylated and/or propoxylated aminoethylated nonylphenol derivatives. These polyols generally find utility in spray applied polyurethane foams. Another example is sucrose-based polyols such as those based on sucrose derivatives and/or mixtures of sucrose and glycerine derivatives condensed with ethylene oxide and/or propylene oxide. These polyols generally find utility in pour-in-place molded foams.
Typical polyols used in the manufacture of flexible polyurethane foams include, but are not limited to, those based on glycerol, ethylene glycol, trimethylolpropane, ethylene diamine, pentaerythritol, and the like condensed with ethylene oxide, propylene oxide, butylene oxide, and the like. These are generally referred to as xe2x80x9cpolyether polyolsxe2x80x9d. Another example is the graft copolymer polyols which include, but are not limited to, conventional polyether polyols with vinyl polymer grafted to the polyether polyol chain. Yet another example is polyurea modified polyols which consist of conventional polyether polyols with polyurea particles dispersed in the polyol.
Examples of polyols used in polyurethane modified polyisocyanurate foams include, but are not limited to, aromatic polyester polyols such as those based on complex mixtures of phthalate-type or terephthalate-type esters formed from polyols such as ethylene glycol, diethylene glycol, or propylene glycol. These polyols are used in rigid laminated boardstock, and may be blended with other types of polyols such as sucrose based polyols, and used in polyurethane foam applications.
Catalysts used in the manufacture of polyurethane foams are typically tertiary amines including, but not limited to, N-alkylmorpholines, N-alkylalkanolamines, N,N-dialkylcyclohexylamines, and alkylamines where the alkyl groups are methyl, ethyl, propyl, butyl and the like and isomeric forms thereof, as well as hetrocyclic amines. Typical, but not limiting, examples are triethylenediamine, tetramethylethylenediamine, bis(2-dimethylaminoethyl)ether, triethylamine, tripropylamine, tributylamine, triamylamine, pyridine, quinoline, dimethylpiperazine, piperazine, N,N-dimethylcyclohexylamine, N-ethylmorpholine, 2-methylpiperazine, N,N-dimethylethanolamine, tetramethylpropanediamine, methyltriethylenediamine, and mixtures thereof
Optionally, non-amine polyurethane catalysts are used. Typical of such catalysts are organometallic compounds of lead, tin, titanium, antimony, cobalt, aluminum, mercury, zinc, nickel, copper, manganese, zirconium, and mixtures thereof Exemplary catalysts include, without limitation, lead 2-ethylhexoate, lead benzoate, ferric chloride, antimony trichloride, and antimony glycolate. A preferred organo-tin class includes the stannous salts of carboxylic acids such as stannous octoate, stannous 2-ethylhexoate, stannous laurate, and the like, as well as dialkyl tin salts of carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate, dioctyl tin diacetate, and the like.
In the preparation of polyisocyanurate foams, trimerization catalysts are used for the purpose of converting the blends in conjunction with excess A component to polyisocyanurate-polyurethane foams. The trimerization catalysts employed can be any catalyst known to one skilled in the art including, but not limited to, glycine salts and tertiary amine trimerization catalysts, alkali metal carboxylic acid salts, and mixtures thereof Preferred species within the classes are potassium acetate, potassium octoate, and N-(2-hydroxy-5-nonylphenol)methyl-N-methylglycinate.
Dispersing agents, cell stabilizers, and surfactants may be incorporated into the present blends. Surfactants, better known as silicone oils, are added to serve as cell stabilizers. Some representative materials are sold under the names of DC- 193, B-8404, and L-5340 which are, generally, polysiloxane polyoxyalkylene block co-polymers such as those disclosed in U.S. Pat. Nos. 2,834,748, 2,917,480, and 2,846,458,.
Other optional additives for the blends may include flame retardants such as tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate, tris(1,3-dichloropropyl)phosphate, diammonium phosphate, various halogenated aromatic compounds, antimony oxide, aluminum trihydrate, polyvinyl chloride, and the like. Other optional ingredients may include from 0 to about 3 percent water, which chemically reacts with the isocyanate to produce carbon dioxide. The carbon dioxide acts as an auxiliary blowing agent.
Also included in the mixture are blowing agents or blowing agent blends as disclosed in this invention. Generally speaking, the amount of blowing agent present in the blended mixture is dictated by the desired foam densities of the final polyurethane or polyisocyanurate foams products. The proportions in parts by weight of the total blowing agent blend can fall within the range of from 1 to about 45 parts of blowing agent per 100 parts of polyol, preferably from about 4 to about 30 parts.
The polyurethane foams produced can vary in density from about 0.5 pound per cubic foot to about 40 pounds per cubic foot, preferably from about 1.0 to about 20.0 pounds per cubic foot, and most preferably from about 1.5 to about 6.0 pounds per cubic foot for rigid polyurethane foams and from about 1.0 to about 4.0 pounds per cubic foot for flexible foams. The density obtained is a function of how much of the blowing agent, or blowing agent mixture, of the invention is present in the A and/or B components, or that is added at the time the foam is prepared.
The HFC-245fa component of the novel azeotrope-like compositions of the invention is a known material and can be prepared by methods known in the art such as those disclosed in WO 94/14736, WO 94/29251, WO 94/29252. The hydrocarbon components are known materials that are available commercially and are used in various grades ranging from 75% to 99% purities. For the purposes of the present invention n-pentane, isopentane, cyclopentane, n-hexane and isohexane refer to all such commercial grades of material.